The Release of QGIS 3.0 was a great success and with the first LTR (3.4) scheduled for release this fall, it is now the perfect time to port your plugins to the new API. QGIS 3.0 is the first major release since September 2013 when QGIS 2.0 was released. During the release cycles of all 2.x releases, the QGIS Python API remained stable. This means that a plugin or script meant to be used in Read more…
Did you know that the possibilities to make a full QGIS back end solution for quality assurance and archiving in PostgreSQL are immense? SQL has it’s well known limitations, but with a little bit creativity you can make quite nice solutions just using triggers and rules. In this post I’ll explain what we did lately based on a project with a customer. He needed to assure the consistency of data but still give his employees the possibility Read more…
Lately, I have been confronted with the need of translating Interlis files (from French to German) to use queries originally developed for German data. I decided to create an automated convertor for Interlis (version 1) Transfer Format files (.ITF) based on the existing cadastral data model from the Swiss confederation (DM01AVCH). The ILI model file conversion has been achieved manually once. This was quite simple since the used model is an extension with little to Read more…
Recently there have been some questions and discussions about python based expression functions and how parameters like usesGeometry need to be used. So I thought I’d quickly write down how this works. There is some intelligence If the geometry or a column is passed in as a parameter you do not need to request it manually, you can even specify explicitly that you do not require the geometry or a column here. @qgsfunction(args=’auto‘, group=’Custom‘, usesGeometry=False, referencedColumns=[]) def Read more…
Expressions in QGIS are more and more widely used for all kinds of purposes. For example the recently introduced geometry generators allow drawing awesome effects with modified feature geometries on the fly. The last days at the QGIS developer meeting 2017, I spent some time looking into and improving the performance for expressions. This was something that was on my todo list for a while but I never got around to working on it. Short Read more…
Lately I’ve been spending time porting a bigger plugin from QGIS 2.8 to 3 while maintaining 2.8 compatibility. You can find it at https://github.com/opengisch/qgis2compat/ and https://plugins.qgis.org/plugins/qgis2compat/ One code to rule them all. My target was to have to edit the source code as little as possible to simulate a lazy or busy coder that has to upgrade his/her plugins. Lots of work has already gone into 2.14 to support PyQt 4 and 5 with the Read more…
Just for the sake of documenting things, when running qgis 2to3 on a plugin I encountered a tricky situation regarding signals. MYQGISDIR/scripts/2to3 -f signals -w my/plugin/path The original code: extra_arg = „my test argument“ QObject.connect( action, SIGNAL( „triggered()“), lambda extra_arg=my_arg: show_extra_arg(extra_arg)) def do_load_project(extra_arg): print extra_arg # „my test argument“ The generated code: extra_arg = „test_arg“ action.triggered.connect( lambda extra_arg=my_arg: show_extra_arg(extra_arg)) def do_load_project(extra_arg): print extra_arg # False so in do_load_project we get False instead of „my test Read more…
Here an example on how to work with threads in a consistent and clean manner in QGIS python plugins
Behind the scenes a lot has happened to get ready for Qt5 and Python3. On the same codebase that is becoming the next release QGIS 2.16. This is really a great thing since we can focus work on a single master branch and I’m very happy that we got so far with this approach already. Testing At OPENGIS.ch we have put a huge effort into getting the Travis CI test infrastructure to test our code with Qt5 Read more…
QGIS 3 is not yet there and there is still plenty of time to prepare and migrate. But I thought I would give some advice about things that you can keep in mind while working on your plugins to make your life easier when you will have to actually do the migration. It’s mostly about making your code prepared for Python 3 and PyQt5. Do not use star imports Don’t do from PyQt4.QtCore import * Read more…